In manually operated electric switches, frequently, it is of importance to prevent switches from being switched on, indexed to the next position or switched in the wrong direction by inadvertence. Various measures are, therefore, taken to prevent an undesirable operation of electric switches. For example, a gear switch has been described in Applicant's Patent Application P 44 39 905.7 wherein a neutral position can be arrested so that an engine gear cannot be clutched or shifted, by inadvertence, from the forward to the rearward direction and vice versa.
Similar problems are also likely to be encountered with manually operated rotary switches in which an actuator can be indexed, by inadvertence, to the next position or rotated in the wrong direction, thereby attaining an undesired switching state. This problem may also be faced with steering column switches wherein a rotary switch actuated by a rotary handle is provided in the actuating lever.
It is the object of the invention to prevent, in a rotary switch of this type, a new switching position from being set by inadvertence.
The invention resides in predetermining the individual rotary positions of the switch by means of suitable locking means. The invention provides a locking ring engaging with the aid of a locking contour, with bias, a conforming locking contour of the support rigidly connected to the casing. The bias can be substantial so that only by intentionally applying substantial force, the next switching step can be performed. Hence, switching or over-switching by inadvertence is not likely to occur. As the locking contour and the conforming contour, preferably, are meshing, the locking contour will first have to be disengaged from the conforming contour in order to enable the next switching step to be taken. The contour can be so selected that the teeth are provided with sloping faces associated to one another which in the event of a rotary movement of the handle automatically result in a disengagement of the locking contour from the conforming contour because the sloping faces of the teeth act as ramps pushing the locking ring out of the conforming contour. However, a rectangular engagement will require a specific disengagement, for example, by longitudinally displacing the handle in order to enable the locking contour to be twisted with respect to the conforming contour.
To limit the number of switching positions (i.e. the number of rotating steps of the rotary switch), the two locking contours associated to one another can be twisted step by step with respect to one another until the stops of locking ring and support rigidly connected to the housing are in abutment with one another.
To attain, in a simple way, the bias desired for automatic engagement, a helical spring, holds the contour of the locking ring in permanent engagement with the conforming contour on the support, wherein - as previously mentioned - due to sloping toothed flanks of the confirming contours, the locking ring through a rotating movement, can be disengaged against the bias so that after exceeding a critical point it automatically locks, under bias, in the next step of the tooth.
The individual teeth of the locking contour can be equidistantly distributed across the front face of a ring which accordingly applies to the conforming contour on the support. The teeth can be of a triangular or sinusoidal configuration unless a rectangular toothing is chosen as previously mentioned.
If it is desired, that the individual rotating steps are to be successively locked by a simple rotating movement and if, in exceptional cases, e.g. in special designs of the switch, the next locking step is to be taken only after a special manipulation, a gate lock is arranged on the support and is axially displaceable and non-rotatable thereon when said support is in a first axial position. The gate lock described therein can thus selectively be assembled in a locking rotary switch if it is to be safeguarded with such a switch that the next step is allowed to be taken only by a special manipulation. Special locking stops can be provided on the locking ring which get into abutment with the gate lock taking a locking position, thereby preventing the locking ring and, hence, the handle from rotating. Also it would be possible for the gate lock itself to engage the tooth flank of the locking ring thereby arresting the same with respect to the support. If the gate valve is to prevent the rotating movement of the handle and, hence, of the locking ring in both rotating directions, the gate lock is moved such that it engages a locking stop on the locking ring from both sides in a fork-type manner, or plunges in a bar-type manner in the interval between two locking stops on the locking ring.
To the extent that the actuating means, i.e. the handle, in the axial direction thereof, is not simultaneously used for permanently switching a sliding contact, a simple axial movement of the actuating means can be adequate to achieve an unlocking position in which the handle can be rotated. Alternatively, it may be advisable, to provide special means, such as an actuating button, on the outer end of the handle, thereby enabling disengagement without operating the handle by displacing the button with respect to the handle longitudinally thereof. To automatically restore the gate lock to its locking position after disengagement and after a new rotating position having been reached, the return movement of the actuating element moves the gate lock into a first axial position. To also avoid disengagement by inadvertence it is suggested, to effect disengagement against the force of a spring in order to prevent the gate lock from automatically getting into its unlocking position by vibratory or the like motion. The locking ring can be of a design such that, through axial displacement of the actuating means, i.e. the handle, it can be placed in its unlocking position in that the actuating means, during its longitudinal displacement, pushes the gate lock in its unlocking position. In this way, the same spring supported on the actuating means to maintain the locking ring in engagement with the conforming contour, at the same time can apply the bias against which the gate lock is to be removed from its locking position. The locking force, hence, is the same force by which the gate lock is actuated.
If the actuating means or the handle is coupled, in the axial direction, to the gate lock, the same helical spring, during release of the handle, will withdraw the gate lock back to its locking position with respect to locking ring.
Frequently, it is desirable that a switch actually suitable for actuating switch contacts by performing a pushing movement in the axial direction be blocked for this type of actuation, or that an axially actuating switch button be prevented from so acting. In such cases, a multifunction switch suitable to switch in the axial rotating direction, is reduced to act as a rotary switch. If desired, a locking element insures that the switch button or the handle is axially displaced in the longitudinal direction, thereby enabling use thereof for actuating contacts in that direction. The locking element can be a simple ring supported on the carrier and being in abutment with suitable faces on the handle or on the actuating button, so that the same can be twisted but not displaced over the front face of the ring.
With the aid of locking contours potential switching positions can be fixed in which the contacts provided can electrically communicate. If only one predetermined switching angle is available for switching functions the said switching angle can be subdivided into individual switching positions by distributing a corresponding number of locking teeth. Accordingly, it is possible with the switch of the invention to take five different switching positions within one switch angle provided, thereby enabling two locking positions in the right-hand rotation and two locking positions in the left-hand rotation to be attained.